Egyptian prosecutors have demanded the maximum penalty, ranging from 15 to 25 years in jail, for all 20 defendants in the trial of al-Jazeera journalists accused of aiding the blacklisted Muslim Brotherhood.

Australian journalist Peter Greste and two other detained reporters with the Qatar-based Al-Jazeera English are among the accused, in a trial that has triggered international outrage amid growing fears of media restrictions in Egypt.

"We request that the court, without compassion or mercy, apply the maximum penalty for the abominable crimes they have committed … mercy for such [people] will bring the entire society close to darkness," prosecutor Mohamed Barakat told the court on Thursday.

The four foreign defendants in the case, including Greste, are charged with "spreading false news", collaborating and assisting the Egyptian defendants in their crimes by providing media material, editing it and publishing it on the Internet and al-Jazeera.

Nine of the 20 defendants are in detention, while others are being tried in absentia, including three foreign reporters who are abroad.

The 16 Egyptians could get prison terms of 25 years, while the four foreigners could be jailed for 15 years, according to defence lawyer Ibrahim Abdel Wahab.